The increased use of miniaturized electronics for data processing, signal processing and electrical component control circuits has required a corresponding increase in the demand for the multi-conductor connectors needed to connect such electronic components together. In some applications, such as in high security areas, in areas particularly sensitive to electromagnetic radiation, and in areas where such radiation might be considered a health hazard, it is necessary to provide electromagnetic shielding for such equipment, for the cables interconnecting such equipment, and for the connectors terminating such cables.
Shielded connectors for multi-conductor cables are well-known. Such connectors must provide a surrounding shell which is conductive in order to shield the internal wires and a mechanism for completing a radiation-tight electrical connection between the metallic shell and the conductive braid or foil surrounding the wires of the cable. Finally, the connector must provide physical attachment of the connector to the cable which does not allow strain on the electrical connection of the wires to the connector terminals nor of the electrical connection of the cable shielding to the connector housing.
It has become common in shielded connector technology to provide such strain relief and such connection to the braid or foil surrounding the cable by peeling the outer insulation layer or jacket away from the braid or foil, folding the braid or foil back over the outer jacket and clamping both the layer of braid or foil and the cable with a bushing or metallic ferrule which completes the electrical circuit between the braid or foil and the conductive connector shell and, at the same time, clamps the cable with sufficient strength to provide strain relief for the electrical connections inside of the connector assembly. Such shielded connector assemblies have become well-known in the art and are typified by A. C. Knack Pat. No. 4,272,148, granted June 9, 1981. Other prior art connector assemblies utilize a metallic ferrule crimped directly over the shielding layer.
Such shielded connector assemblies of the prior art have had several difficulties. In the first place, the steps of peeling back the outer insulator layer and folding back the conductive braid or foil are time-consuming and require a great deal of dexterity. Moreover, the exposed braid or foil is fragile and often tears either in the act of folding it back over the outer insulative layer, or as a result of the shearing forces generated when crimping during assembly. Since the braid or foil is directly clamped, all of the strain relief forces are transmitted through the braid or foil, again causing the braid or foil to tend to tear or distort in use. Once torn or distorted, the braid or foil can no longer provide a complete and continuous electromagnetic shielding for the connector-cable combination. A torn braid or foil also loses some of its ability to provide adequate strain relief. As a result, prior art shielded connectors often fail, either in providing adequate shielding, or in providing adequate strain relief, or in both, either initially, due to lack of care in assembling the connector to the cable, or during use, due to damage done while relieving strain on the electrical connections during plugging and unplugging operations. Moreover, such prior art connector assemblies required considerable time and expertise in order properly to assemble the parts.